EP1789787A1 - Protein cleavage at aspartic acid using chemical reagents - Google Patents
Protein cleavage at aspartic acid using chemical reagentsInfo
- Publication number
- EP1789787A1 EP1789787A1 EP05787084A EP05787084A EP1789787A1 EP 1789787 A1 EP1789787 A1 EP 1789787A1 EP 05787084 A EP05787084 A EP 05787084A EP 05787084 A EP05787084 A EP 05787084A EP 1789787 A1 EP1789787 A1 EP 1789787A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- polypeptide
- hydrolyzing
- composition
- composition according
- sequence
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K33/00—Medicinal preparations containing inorganic active ingredients
- A61K33/42—Phosphorus; Compounds thereof
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/68—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving proteins, peptides or amino acids
- G01N33/6803—General methods of protein analysis not limited to specific proteins or families of proteins
- G01N33/6848—Methods of protein analysis involving mass spectrometry
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K33/00—Medicinal preparations containing inorganic active ingredients
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07K—PEPTIDES
- C07K1/00—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length
- C07K1/12—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length by hydrolysis, i.e. solvolysis in general
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07K—PEPTIDES
- C07K1/00—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length
- C07K1/12—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length by hydrolysis, i.e. solvolysis in general
- C07K1/128—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length by hydrolysis, i.e. solvolysis in general sequencing
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/483—Physical analysis of biological material
Definitions
- the present invention provides a method of processing proteins for identification and quantification.
- the invention relates to a kit and an apparatus for processing proteins into peptides by using chemical reagents, and to the methods of using them in broad range of proteomics researches.
- the platforms used for proteomic analysis involve the integration of two broad practices, including separation and identification of proteins in a sample.
- Two-dimensional gel electrophoresis (2-DE) or liquid chromatography (LC) of one or more types are used for the separation of proteins prior to mass spectrometry.
- 2-DE the proteins placed in a gel migrate depending largely on molecular weight and isoelectric point, thus generating a characteristic gel pattern.
- Mass spectrometry is generally used for the identification of proteins.
- proteins or peptides are ionized and ionized species are subject to electric and/or magnetic fields in a vacuum. Their molecular weights can be deduced from the travel path of the ions.
- the identities of proteins or peptides can be disclosed by a peptide fingerprinting method or de novo sequencing using mass spectrometry (MS) or tandem MS (MS/MS).
- the proteins are enzymatically cleaved into their constituent peptides prior to MS analysis to enhance the likelihood that at least some of the protein is sufficiently ionized so as to be detected by generating the peptides compatible for an accurate analysis in general MS apparatus which has a limited ranges of mass measurement.
- Peptide mass mapping of proteins separated by polyacrylamide gel electrophoresis with enzymatic digestion has been a routine procedure for protein characterization.
- the most frequently used protease is trypsin because of its well-defined specificity and the appropriate size of tryptic peptides for mass spectrometric analysis.
- proteases such as Lys-C, GIu-C, and Asp-N are discriminated against certain substrates. Having a lot of strong points, tryptic digestion is not a method of choice for hydrophobic or very basic proteins.
- protease autolysis products for example, trypsin; 261.14, 514.32, 841.50, 905.50,1005.48, 1044.56, 1468.72, 1735.84, 1767.79, 2157.02, 2210.10, 2282.17, 3012.32, 4474.09, 4488.11 Da
- some buffers required for efficient and specific proteolysis may generate chemical noises, thus requiring additional purification before mass spectrometric analysis.
- an “isotope tag” refers to a chemical moiety having suitable chemical properties for incorporation of an isotope, allowing the generation of differentially tagged polypeptides in two samples.
- the isotope tag also has an appropriate composition to allow incorporation of a stable isotope at one or more atoms.
- a particularly useful stable isotope pair is hydrogen and deuterium, which can be readily distinguished using mass spectrometry, for example, 13C, 15N, 17O, ISO or 34S.
- Amino acid-specific methods such as ICATTM have the advantage of reducing sample complexity but have the disadvantage of discriminating against proteins with low number of cysteines.
- Proteins can be also isotopically labeled at the C-termini of the tryptic peptides.
- One method of global labeling inserts an isotopic label via the molecule of water that is incorporated into peptides during cleavage of amide backbones by enzyme.
- ESI electrospray ionization
- MALDI matrix-assisted laser desorption/ionization
- the practice of 18O- labeling is receiving increasing attention as a preferred method for heavy isotope labeling and several examples of its application have been published. It is common practice and considered advantageous to use the highest enrichment of H218O as possible in order to achieve the highest degree of labeling of each proteolytic fragment
- Figure 1 is a flow chart for the identification of proteins by proteomic analysis using protein cleavage at aspartic acid (PCA) method.
- PCA protein cleavage at aspartic acid
- Figures 2A, 2B, and 2C are MALDI-MS and MALDI-TOF/TOF analysis of BSA (Bovine Serum albumin) by PCA method. Spectra were obtained utilizing an Applied Biosy stems 4700 Proteomics AnalyzerTM: Panel A; MALDI mass spectra (mass range 800-4300Da); Panel B; Database search results by PMF with MASCOTTM; Panel C; For MS/MS(MALDI-TOF/TOF) analyses of the 1723.86 Da monoisotopic peak, spectra were obtained by the accumulation of 5000 consecutive laser shots at a collision energy of IkV with air serving as the collision gas.
- Figures 3A and 3B are MALDI-MS analysis of Ubiquitin by PCA method.
- Spectra were obtained utilizing Applied Biosystems 4700 Proteomics AnalyserTM: Panel A; MALDI mass spectra (mass range: 400-4300Da); Panel B; Database search results by PMF (peptide mass fingerprint) with MASCOTTM.
- Figures 4A, 4B and 4C are database search results with MASCOTTM: Protein sample; (BSA) Bovine Serum Albumin; Panel A; Database search result with MALDI-TOF mass list (above S/N 10) of BSA digested through PCA method. [Sequence coverage: 40%]; Panel B; Database search result with MALDI-TOF mass list (above S/N 10) of BSA digested by trypsin. [Sequence coverage: 32%]; Panel C; Database search result with MALDI-TOF mass list (above S/N 10) obtained by combination PCA method and tryptic digestion. PCA/trypsin method's database search result shows high sequence coverage [87%]
- Figure 5 shows detergent-free and Chaotropic reagent-free chemical digestion of membrane proteins.
- De-lipidated membrane protein aggregates obtained from mouse brain lipid raft were digested in PCA solution (15(v/v)% of acetic acid (pH 2.0), 30(v/v)% of acetonitrile, and TCEP (1OmM)) were incubated at
- FIG. 6 shows UV chromatogram from a reverse-phase HPLC separation of the hydrolysate obtained from PCA reaction of de-lipidated membrane protein aggregates. About lmg of the protein hydrolysate was injected. Pooled fractions were indicated by the circled number.
- Figures 7A, 7B and 7C are MALDI-TOF/TOF detection of ubiquitin by PCA method: Panel A; MS spectra of ubiquitin processed by PCA method; Panel B; MS spectra of ubiquitin obtained by PCA-DMT (Differential Mass Tagging) method;
- Panel C and D 1:1 and 1:2 mixture of PCA/PCA-DMT cleaved ubiquitin.
- Figure 8 shows the result of LC-MS/MS experiment using the hydrolysates obtained from sequential digestion of mouse brain lipid raft by PCA and Trypsin: Panel A; Total ion chromatogram of tryptic hydrolysate of each pooled fraction in
- FIG. 4 Each pooled fraction was indicated by circled number ;Panel B; Extracted ion chromatogram at a marked time in panel A ; Panel C; Tandem MS/MS result of the ion circled in panel B.
- Figure 9 is an assignment of the mass of peptide fragments of ubiquitin obtained by PCA method [sequence coverage is 100%]
- Figures 1OA and 1OB are an assignment of the mass of observed peptide fragments of BSA (Bovine Serum Albumin) by PCA method.
- BSA Bovine Serum Albumin
- the peptide mass list obtained from MALDI-TOF and the identities of some peptide were verified from de novo sequencing by tandem MS.
- Figures HA and HB are the selected list of mouse brain lipid raft proteins identified by LC-MS/MS of the hydrolysates obtained from sequential digestion by
- An objective of this invention is to provide the method, kit, and apparatus for acid hydrolysis of proteins, which can guarantee the strict specificity of cleavage at aspartyl residue without the production of unpredictable modification of the peptides.
- the invention provides the optimal composition of reagents for acid hydrolysis of proteins, referred to herein as protein cleavage at aspartic acid (PCA), for protein identification and quantification.
- PCA protein cleavage at aspartic acid
- the identification of proteins in a given sample can be achieved by de novo sequencing of the peptides generated or by peptide mass fingerprinting from MS analysis results by accommodating newly developed rules of fragmentation.
- the present invention includes the designing of apparatus for PCA, which is developed for incubating the solution above 95°C with minimizing the loss of vapor pressure by heating the lid as well as bath simultaneously in the same temperature.
- the present method provides handy and simple procedure for processing of proteins prior to MS analysis comprising of just a few hours of incubation and sample dry.
- PCA can be used in combination with tryptic digestion to generate the peptides suitable for tandem MS analysis in order to get enough information for the detailed structural analysis of proteins.
- the invention further provides methods for quantifying proteins in a sample by adopting the concept of 18 O-labeling of proteins using H2 18 O during hydrolysis for comparative proteomics.
- the present invention provides a polypeptide hydrolyzing composition
- a polypeptide hydrolyzing composition comprising an acid component water miscible organic solvent and a reducing agent.
- the acid component is trifluoroacetic acid, phosphoric acid, propionic acid, HCl, o-iodobenzoic acid, glacial acetic acid, or any acid having buffering capacity near pH 2.
- the acid component can be a mixture of trifluoroacetic acid, phosphoric acid, propionic add, HCl, and o-iodobenzoic acid.
- pH of hydrolyzing solution at time of reaction is in the range of 1.5 to 2.5
- the hydrolyzing solution comprises at least 2 to 30(v/v)% glacial acetic acid.
- the hydrolyzing solution comprises 15(v/v)% glacial acetic acid, pH 2.0.
- the water miscible organic solvent is Acetonitrile, DMF (Dimethyl formamide), DMSO (Dimethylsulfoxide), THF (Tetrahydrofurane), or an alcohol.
- the alcohol is methanol or ethanol.
- the water miscible organic solvent is at least 5-70(v/v)% Acetonitrile, preferably 30(v/v)% Acetonitrile.
- the reducing agent is TCEP (Tris(2-carboxyethyl)phosphine) / DTT (Dithiothreitol), or beta-Mercaptoethanol.
- the reducing agent is phosphine compound which can work at acidic pH range (1.5-2.5) such as TCEP (Tris(2- carboxyethyl)phosphine).
- the reducing agent is at least ImM-IM TCEP (Tris(2- carboxyethyl)phosphine) or DTT (Dithiothreitol).
- the reducing agent is at least 10 mM TCEP (Tris(2-carboxyethyl) ⁇ hos ⁇ hine) or DTT (Dithiothreitol).
- the composition comprises about 2-30(v/v)% acetic acid of the hydrolyzing solution, about 5-70(v/v)% acetonitrile of the hydrolyzing solution, and about ImM-IM of TCEP ((Tris(2-carboxyethyl)phosphine).
- the composition comprises about 15(v/v)% of acetic acid of the hydrolyzing solution, acetonitrile at an amount of about 5-70(v/v)% of acetonitrile of the hydrolyzing solution, and about ImM-IM of TCEP ((Tris(2-carboxyethyl)phosphine).
- the composition comprises about 15(v/v)% of acetic acid of the hydrolyzing solution, about 30(v/v)% of acetonitrile of the hydrolyzing solution, and about ImM-IM of TCEP ((Tris(2-carboxyethyl)phosphine).
- the composition comprises about 15(v/v)% of acetic acid of the hydrolyzing solution, about 30(v/v)% acetonitrile of the hydrolyzing solution, and 1OmM of TCEP ((Tris(2-carboxyethyl)phosphine).
- the composition may not include the water miscible organic solvent and a reducing agent.
- the composition may not include the water miscible organic solvent or the reducing agent.
- composition of the present invention can include a detergent which is OBG (octyl-beta-glucopyranoside) or SDS(Sodium dodecyl sulfate).
- OBG octyl-beta-glucopyranoside
- SDS Sodium dodecyl sulfate
- the present invention provides a method for hydrolyzing a polypeptide at an aspartic acid amino acid residue comprising contacting the polypeptide with a hydrolyzing solution of the present invention to obtain polypeptide fragments having aspartic acid residue at the N- or C- terminus and optionally determining amino acid sequence of resultant polypeptide fragments.
- a method of determining amino acid sequence of a polypeptide comprises:
- the sequence of polypeptide fragments is determined through mass spectrometry. Water is labeled with deuterium, or tritium, or 17 O, or 18 O labeled water.
- the hydrolysis of the polypeptide is carried out in a reaction temperature in the range of about 75 to 15O 0 C.
- the container material for hydrolysis reaction is made of plastic which is made of polyethylene, polypropylene, high density polyethylene, or low density polyethylene.
- the reaction heat is created by micro wave, or ultra sonic wave.
- the sequence of the polypeptide can be determined by a database search using a modified cleavage rule incorporating polypeptide fragments having aspartic acid residues at either the N- or C-terminal ends or both the N- and C- terminal ends.
- the database search is carried out with PCA database menu which has a cleavage rule and modification rule incorporating polypeptide fragments having aspartic acid residues at either the N- or C-terminal ends or both the N- and C-terminal ends.
- a method of determining amino acid sequence of a polypeptide comprises:
- step (1) hydrolyzing the composition obtained in step (1) with the composition to obtain polypeptide fragments having aspartic acid residue at the N- or C- terminal ends of the fragments;
- sequence of the polypeptide can be determined by a database search using a modified cleavage rule incorporating polypeptide fragments having aspartic acid residues at either the N- or C-terminal ends or both the N- and C- terminal ends.
- the database search is carried out with PCA database menu which has a cleavage rule and modification rule incorporating polypeptide fragments having aspartic acid residues at either the N- or C-terminal ends or both the N- and C-terminal ends.
- a kit for hydrolyzing polypeptide comprises (i) a container containing an acid solution and water; (ii) a container containing a water miscible organic solvent and a reducing agent.
- the reducing agent can be omitted.
- PCA Protein cleavage at Aspartic add
- PCA This invention
- PCA solution and the mass pattern and the sequence of amino acid of the resulting peptides can be analyzed by mass spectrometer.
- Proteins dissolved in solvents or in gel band are incubated at the temperature higher than 95°C (Incubation at 99.9°C is preferable) for more than 10 minutes in the presence of PCA solution.
- Acid trifluoroacetic acid, phosphoric acid, propionic acid, HCl, o- iodobenzoic acid, glacial acetic acid, Formic acid, (Acid such as acetic acid that has a buffering capacity near pH 2 but do not bring about any unexpected modifications during reaction is preferable.)
- Water miscible organic solvent Acetonitrile, DMF (Dimethyl formamide), DMSO (Dimethylsulfoxide), THF (Tetrahydrofurane), any kinds of alcohol such as methanol and ethanol, (The amount of acetonitrile is preferably 30(v/v)%.)
- Reducing agent for disulfide bond TCEP (Tris(2- carboxyethyl)phosphine), DTT (Dithiothreitol),
- Reducing agent such TCEP that can work at acidic pH range is preferable.
- reaction in the presence of 15% acetic acid (2.62mM), 30(v/v)% acetonitrile and TCEP (1OmM) is optimal for protein cleavage at aspartic acid and reduction of disulfide bond in proteins.
- the sample was then cooled to room temperature and the reaction solution was dried in the same reaction tube without transferring to a new tube for speed- vac dry.
- the dried peptide extract was diluted with appropriate volume of 0.1(v/v)% TFA.
- Desalting process for removing TCEP oxide (TCEPO) and other salts which can interfere with mass analysis can be done by the passage through ⁇ - C18 ZipTips.
- the resulting peptides are analyzed by mass spectrometer.
- Bovine Serum Albumin (BSA, Calbiochem Catalog No. 126609) is used to verify the usefulness of PCA method for sample preparation.
- the reaction was carried out at 99.9 0 C for 2hrs in the presence of PCA solution (15(v/v)% of acetic acid (pH 2.0), 30(v/v)% of acetonitrile, and 1OmM TCEP).
- PCA solution 15(v/v)% of acetic acid (pH 2.0), 30(v/v)% of acetonitrile, and 1OmM TCEP).
- Any optional modifications except for pyro-glu E (N-term) and pyro-glu Q (N-term) were not observed in the mass spectra obtained. These optional modifications do not interfere with the identification of proteins by MASCOTTM.
- DTT dithiothreitol
- TCEP Tris(2-carboxyethyl)phosphine
- ubiquitin Sigma Catalog No. U6253
- the reaction was carried out at 99.9 0 C for 2hrs in the presence 15(v/v)% of acetic acid having pH 2.0 and 30(v/v)% of acetonitrile.
- TCEP is not included in the reaction mixture due to the lack of disulfide bond in ubiquitin.
- Cleavage of ubiquitin with the PCA method resulted in perfect coverage, 100% ( Figure 3). Tryptic digestion retrieved about 82% of sequence of ubiquitin, but another variant of ubiquitin was picked up by MASCOTTM.
- the peptides bound to the ZipTip were eluted out sequentially in 5 ⁇ L each of 20(v/v)%, 50(v/v)% and 80(v/v)% ACN in 0.1(v/v)% HAc (acetic acid) solution or just 50(v/v)% ACN/0.1(v/v)% HAc.
- the sequentially peptide solution was dried to reduce its volume to about 5 ⁇ L and a matrix solution was added for MALDI-TOF analysis.
- the purpose of using ZipTip is to remove salts from the sample prior to MS detection. This approach was applied to characterization of proteins such as BSA (bovine serum albumin) resulting in improved identification with high sequence coverage (87%) comparing with 40% and 32% obtained by PCA method and tryptic digestion, respectively as shown in Figure 4.
- BSA bovine serum albumin
- proteomic analysis of membrane proteins has been indispensable and challenging subject for understanding of diverse signaling networks and for discovering targets for a given disease.
- Most of researchers have relied on classical proteomic method consisted of two-dimensional electrophoresis for separating proteins prior to enzymatic digestion and mass spectrometric analysis, while only few studies have been reported by accommodation of gel-free LC-MS/MS technologies.
- gel-free LC-MS/MS technologies depend on detergents or chaotropic reagents to isolate the integral proteins from membrane fraction.
- CCPA method Chemical Cleavage of Proteins at Aspartic acid
- Lipid raft was selected for proving the usefulness of chemical digestion, because lots of proteomic studies have been performed to elucidate the composition of proteins in lipid raft.
- Lipid raft was prepared as described in Proteomics 2004, 4, 3536-3548.
- Mouse brains were homogenized 20 times with a tight Dounce homogenizer (Kontes, Vineland, NJ, USA) in the lysis buffer (l(v/v)% Triton X-100, 25 mM HEPES, pH 6.5, 150 mM NaCl, 1 mM EDTA, 1 mM PMSF, and protease cocktail (Roche Molecular Biochemicals, Indianapolis, IN, USA)), and incubated at 4oC for 20 min.
- lysis buffer l(v/v)% Triton X-100, 25 mM HEPES, pH 6.5, 150 mM NaCl, 1 mM EDTA, 1 mM PMSF, and protease cocktail (Roche Molecular
- the extract was mixed with 2.5 M sucrose, transferred to an SW41 centrifuge tube, and overlaid with 30(w/v)% sucrose solution and 5(w/v)% sucrose solution containing 25 mM HEPES, pH 6.5, and 150 mM NaCl.
- the discontinuous sucrose gradients were centrifuged for 18 h at 4oC in an SW41 rotor at 39 000 rpm. The gradient was fractionated into 12 fractions from the bottom to the top.
- the lipid raft fractions were washed with washing buffer (25 mM HEPES, pH 7.4, 150 mM NaCl) by ultracentrifugation (20 000 rpm, 30 min, 47C), and suspended with 50 mM sodium bicarbonate. By the treatment with acetone and successive washing steps, the precipitate of membrane was obtained. The resulting protein precipitated was dried.
- the dried 9 fractions were incubated with 1/50 amount of Trypsin in the presence of 5OmM Ammonium Bicarbonate at 37oC for 12 hrs.
- the resulting peptides were analyzed by LC-MS/MS.
- Proteins dissolved in water or dried gel band are heated at 99.9 0 C for 2hrs in the presence of PCA solution (15(v/v)% acetic acid (pH 2.0), 30(v/v)% acetonitrile, and 1OmM TCEP).
- PCA solution 15(v/v)% acetic acid (pH 2.0), 30(v/v)% acetonitrile, and 1OmM TCEP.
- 16O- water was replaced by 18O- water.
- the sample was then cooled to room temperature and the reaction solution was dried at 99.9 °C in reaction tube and dissolved with 5 ⁇ L 0.1(v/v)% TFA, and salt was removed by desalting process using ⁇ -C18 ZipTips.
- the peptides bound to the ZipTip were eluted out sequentially in 5 ⁇ L each of 20(v/v)%, 50(v/v)% and 80(v/v)% ACN in 0.1 (v/v) HA ⁇ cetic acid) solution or just 50(v/v)% ACN/0.1(v/v)% HAc.
- the sequentially peptide solution was dried to reduce its volume to about 5 ⁇ L and a matrix solution was added for MALDI-TOF analysis.
- Figure 7 One of the examples is shown in Figure 7.
- signal intensity of monoisotopic mass obtained through the chemical cleavage in the case of using 18O-water is described as S18(M0), and that obtained by mixing the products prepared from separate chemical cleavage reaction in the presence of 16O-water or 18O- water is presented as S16+18(MO).
- Kl indicates the coefficient for the incorporation of one atom of oxygen in chemical cleavage reaction done in the presence of l ⁇ O-water, and K2 for the incorporation of two atoms of oxygen. By calculating the sum of Kl and K2, relative comparison of the amounts of proteins in two different samples can be achieved. In mathematical terms, Kl and K2 can be extracted from the formula as followed.
- the ratio of the peptides obtained by the chemical cleavage reaction of ubiquitin in the presence of 16O- water and 18O- water is calculated as 1:0.65.
- the difference of calculated ratio from theoretical one can be due to the usage of 18O- water containing around 5% of 160-water, the possible contamination of 16O- water in other reagents such TCEP and sample (Ubiquitin), and incorporation of 16O-water from air during the course of reaction.
- the dried peptide extract was suspended in 5 ⁇ L 0.1(v/v)% TFA and desalted with ⁇ -C18 ZipTips.
- the peptides bound to the ZipTip were eluted out sequentially in 5 ⁇ L each of 20(v/v)%, 50(v/v)% and 80(v/v)% acetonitrile in 0.1(v/v)% acetic acid solution or just 50(v/v)% acetonitrile/0.1(v/v)% acetic acid.
- the sequentially peptide solution was dried to reduce its volume to about 5 ⁇ L and a matrix solution was added.
- the purpose of using ZipTip is to remove salts form the samples prior to MS detection, but it does not completely remove the n-OG, a nonionic detergent.
- the two-layer sample deposition method with ⁇ -CHCA as matrix was used in the MALDI-MS analysis.
- the first layer was prepared as a 20mg/mL ⁇ -CHCA solution in 20(v/v)% methanol/acetone ⁇ -CHCA and the second layer with a saturating solution of matrix in 30(v/v)% methanol/water.
- the second layer was added to the Zip-Tipped peptide mixture for producing the ratio of matrix to analyte to 4:1 and the mixture vortexed.
- 0.5 ⁇ L of the first layer was deposited on the sample probe and air-dried, 0.5 ⁇ L of the second layer was deposited on top of the first layer, allowed to air-dry and washed twice with l ⁇ L water.
- the matrix solution was a lOmg of ⁇ -CHCA in 50(v/v)% acetonitrile in water. Aliquots of 0.5 ⁇ L of the peptide mixture and 0.5 ⁇ L of the matrix solution were mixed on the sample plate and air-dried prior to analysis.
- MS/MS data acquisition form the plates (LC-MALDI plates) on which the LC eluent had been spotted by the ProbotTM was performed in a four step process. First, MS spectra were recorded from each of the six calibration spots, and the default calibration parameters of the instrument and the appropriate model of plate model were updated. Second, MS spectra were recorded for all 144 sample spots on that plate. Each spectrum was generated by accumulating the data from
- MS spectra were analyzed using the Peak Picker software supplied with the instrument. Spectral peaks that met the threshold criteria and were not on the exclusion list were included in the acquisition list for the MS/MS portion of the experiment.
- the threshold criteria were set as follows: mass range: 650 to 4000Da; minimum cluster area: 500; minimum signal-to-noise (S/N): 10; Peaks/spot: 30; maximum precursor gap: 200ppm; maximum fraction gap: 4.
- S/N minimum signal-to-noise
- Peaks/spot 30; maximum precursor gap: 200ppm; maximum fraction gap: 4.
- a mass filter excluding matrix cluster ions was applied.
- An XML file was generated that contains the list of the precursor masses selected for MS/MS and their corresponding spot numbers.
- the list was imported into the 4700 Explorer software batch editor, and MS/MS spectra were recorded using air as the collision gas with IkV collision energy setting.
- a method with a stop condition was used. In this method, a minimum of 750 shots (6 sub- spectra accumulated from 125 laser shots each) and a maximum of 2000 shots were allowed for each spectrum. The accumulation of additional laser shots was halted whenever at least 10 ions with a S/N of at least 10 were present on the accumulated MS/MS spectrum, in the region from m/z 400 to 90% of the precursor mass.
- PCA/Trypsin-cleaved peptides were eluted from the nano LC system, Agilent 1100 (Agilent), and ions were sprayed directly into the orifice of a QSTAR- XL quadrupole time-of-flight (TOF) hybrid MS (PE-Sciex, Thornhill, Ontario, Canada).
- TOF time-of-flight
- Proteins were identified by LC/MS/MS by information-dependent acquisition of fragmentation spectra for multiply charged peptides that were then searched against the Human International Protein Index database (ftp://ftp.ebi.ac.uk/pub/databases/IPI/current/MOUSE) by using MASCOT (Matrix Science, London). The following search parameters were used in all MASCOT searches: maximum of two missed CCPA-trypsin cleavage, cysteine carbamidomethylation, methionine oxidation, and a maximum 0.2-Da error tolerance in the MS and 0.1-Da in the MS/MS data. Significant matches with the highest MOWSE scores were considered potential identification.
- Kit for PCA method can be supplied as a set of solution (solution A and solution B) and container designed for optimal heat transfer and for minimizing sample loss during chemical reaction (thin-wall tube for PCR reaction) is highly recommended.
- the reaction should be carried out in the heating apparatus designed for minimizing the loss of vapor pressure by heating the lid as well as bath simultaneously in the same temperature such as PCR machine for better performance.
- Mixture of peptide can be included as internal mass standard.
- 21.4(v/v)% acetic acid in 18O-Water can be used.
- Matrix-assisted laser desorption/ionization-quadrupole ion trap-time of flight mass spectrometry sequencing resolves structures of unidentified peptides obtained by in-gel tryptic digestion of haptoglobin deribatives from human plasma proteomes.
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US61030604P | 2004-09-15 | 2004-09-15 | |
PCT/KR2005/003042 WO2006031063A1 (en) | 2004-09-15 | 2005-09-14 | Protein cleavage at aspartic acid using chemical reagents |
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EP1789787A1 true EP1789787A1 (en) | 2007-05-30 |
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EP05787084A Withdrawn EP1789787A1 (en) | 2004-09-15 | 2005-09-14 | Protein cleavage at aspartic acid using chemical reagents |
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US (1) | US20080318262A1 (en) |
EP (1) | EP1789787A1 (en) |
JP (1) | JP2008513769A (en) |
KR (1) | KR20070063550A (en) |
WO (1) | WO2006031063A1 (en) |
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WO2008128029A2 (en) * | 2007-04-12 | 2008-10-23 | Battelle Memorial Institute | Solution fragmentation systems and processes for proteomics analysis |
CN101696231B (en) * | 2009-09-29 | 2012-09-05 | 刘日廷 | Antigen epitope minimum motif peptide of human papilloma virus 58 type E6 protein |
CN101914134B (en) * | 2010-08-17 | 2013-06-19 | 刘日廷 | Linear epitope minimum motif peptide of human papilloma virus type 58 E7 protein |
FR2990217B1 (en) | 2012-05-03 | 2016-02-05 | Biomerieux Sa | PROCESS FOR OBTAINING PEPTIDES |
CN112985970B (en) * | 2021-03-01 | 2023-03-28 | 上海屹尧仪器科技发展有限公司 | Method for rapidly hydrolyzing protein in dairy product by using inflatable microwave digestion device |
-
2005
- 2005-09-14 EP EP05787084A patent/EP1789787A1/en not_active Withdrawn
- 2005-09-14 WO PCT/KR2005/003042 patent/WO2006031063A1/en active Application Filing
- 2005-09-14 JP JP2007532237A patent/JP2008513769A/en active Pending
- 2005-09-14 US US11/575,089 patent/US20080318262A1/en not_active Abandoned
- 2005-09-14 KR KR1020077008575A patent/KR20070063550A/en not_active Application Discontinuation
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Also Published As
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WO2006031063A1 (en) | 2006-03-23 |
JP2008513769A (en) | 2008-05-01 |
US20080318262A1 (en) | 2008-12-25 |
KR20070063550A (en) | 2007-06-19 |
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